Hydraulic actuator having a self-aspirating actuator rod seal

ABSTRACT

A hydraulic actuator in which an absorbent material is carried by the actuator housing at the interface between it and the actuator rod to capture fluid leaking from the operating chamber. The fluid captured by the absorbent material is drawn therefrom and is directed to a reservoir in response to the reciprocal movement of the actuator rod relative to the housing.

United States Patent [191 Schindel HYDRAULIC ACTUATOR HAVING A SELF-ASPIRATING ACTUATOR ROD SEAL [75] Inventor: Arnold Schindel, Fairlawn, NJ.

[73] Assignee: The Singer Company, Little Falls,

[22] Filed: Nov. 9, 1973 [21] Appl. No.: 407,351

[52] U.S. Cl. 92/86 [51] Int. Cl. F01b 31/00 [58] Field of Search 92/86; 308/363 [56] References Cited UNITED STATES PATENTS 654,761 7/1900 Palm 92/86 1,488,683 4/1924 Jurvjgk 92/86 X 2,000,265 5/1935 Vickers 92/86 X 2,526,236 10/1950 Ingres 92/86 X 2,631,433 3/1953 Thomas 92/86 X 2,898,867 8/1959 Saalfrank I. 92/86 X Mar. 11,1975

3,145,659 8/1964 Svendsen 92/86 X 3,293,994 l2/l966 Napolitano 92/86 3,415,581 12/1968 Seubert 308/363 3,515,033 6/1970 Geyer 92/86 X 3,768,371 10/1973 Orme 92/86 X FOREIGN PATENTS OR APPLICATIONS 913,908 12/1962 Great Britain 308/363 Primary Examiner-Irwin C. Cohen Assistant Examiner-Abraham Hershkovitz Attorney, Agent, or FirmT. W. Kennedy [57] ABSTRACT A hydraulic actuator in which an absorbent material is carried by the actuator housing at the interface between it and the actuator rod to capture fluid leaking from the operating chamber. The fluid captured by the absorbent material is drawn therefrom and is directed to a reservoir in response to the reciprocal movement of the actuator rod relative to the housing.

5 Claims, 1 Drawing Figure HYDRAULIC ACTUATOR HAVING A SELF-ASPIRATING ACTUATOR ROD SEAL BACKGROUND OF THE INVENTION This invention relates to hydraulic actuators and, more particularly, to such actuators in which an actuator rod reciprocates relative to its housing in response to fluid being selectively introduced into an operating chamber formed in the housing.

In these type actuators various techniques have been proposed to reduce the leakage of the operating fluid from the operating chamber. Although some proposals, such as the use of a hermetically sealed rod and a vented bellows, have been very satisfactory in certain circumstances, they suffer from the standpoint that they occupy a relatively large space and do, in fact, permit a relatively low amount of leakage. As a result, these deficiencies render this type of arrangement unsatisfactory in certain other circumstances such as in situations where the actuator is used in conjunction with an optical system, where space and/or the supply volume is limited, or where contamination of materials being externally handled must be avoided.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a hydraulic linear actuator which incorporates a hermetically sealed rod and bellows arrangement and the attendant advantages associated therewith, yet minimizes the disadvantages discussed above.

It is a further object of the present invention to provide an improved sealing arrangement for a hydraulic actuator which occupies a relatively small space and which reduces seal leakage below conventional levels.

Toward the fulfillment of these and other objects, the assembly of the present invention comprises a housing defining an operating chamber, an actuator rod disposed in said operating chamber, means to introduce fluid into said operating chamber in a manner to reciprocate said rod relative to said housing, absorbent means supported by said housing for absorbing fluid from said operating chamber, a storage chamber associated with said housing, means responsive to movement of said rod in one direction for directing fluid from said absorbent means to said storage chamber,

and means responsive to movement of said rod in the opposite direction for directing said fluid from said storage chamber externally of said housing.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a partial vertical cross-sectional view depicting a hydraulic actuator embodying features of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring specifically to the drawing, the reference numeral refers in general to a housing having a central bore 12 extending therethrough and an enlarged cylindrical chamber 14 communicating with the bore and extending coaxially therewith.

An actuator rod is disposed within the housing 10 and includes a stem portion 16 slidably mounted within the bore 12, and a piston portion 18 integral with the stem portion and movably mounted in the cylindrical chamber 14.

An operating chamber 20 is defined between one face of the piston portion 18 and the housing 10 while an operating chamber 22 is defined between the other face of the piston portion and an end plate or the like attached to the housing and not shown for the convenience of presentation. An O-ring seal 24 fits within a groove formed in the outer surface of the piston portion 18 and acts against the wall defining the chamber 14 to seal against fluid leakage between the chambers 20 and 22.

Pressurized fluid is selectively introduced and drawn from the chambers 20 and 22 by means of a control assembly, shown in general by the reference numeral 26, which is connected to the respective chambers by means of ports 28 and 30 and lines 32 and 34, respectively. The control assembly 26 operates to introduce pressurized fluid to the line 32 and, into the operating chamber 20 via the port 28 to force the piston in a direction from right to left as viewed in the drawing. Reversal of the operation of the control assembly 26 will cause the above high pressure fluid to be withdrawn from the chamber 20 and introduced into the chamber 22 via the line 34 and the port 30, to effect movement of the piston 18 in a direction from left to right as viewed in the drawing. Since the control assembly 26 may be of a conventional design and does not form any portion of the present invention, it will not be described in any further detail.

A pair of seal assemblies 36 and 38 are respectively provided in spaced grooves formed in the wall defining the bore 12. The seal assemblies 36 and 38 may be of any conventional design and, for the purposes of illustration, are shown as consisting of a sealing cap adapted to engage the stem portion 16 of the actuator rod and an O-ring extending over the cap.

A port 40 is provided through the housing 10 between the seal assemblies 36 and 38 and registers at one end with the bore 12 and at the other end with a conduit 41 which, in turn, is adapted for connection to a fluid reservoir (not shown) maintained at a relatively low pressure. As a result, upon failure of the seal assembly 36, the fluid leakage from the operating chamber 20 would bypass to the reservoir through the port 40 and the conduit 41 leaving a relatively low pressure differential across the seal assembly 38 and resulting in relatively low leakage across the latter assembly.

The present invention is designed to further minimize leakage across the seal assembly 38. To this end, a wick 42 in the form of an annulus of absorbent material is provided in a groove formed in the inner wall of the housing defining the bore 12, with the inner wall of the wick being in a sealing relation to the stem portion 16 of the actuator rod. The wick 42 is secured in the groove by means of a plate 43 which is disposed in an appropriate cut-out provided in the housing 10 and is secured to the housing by means of a plurality of screws 44. A sealing ring 46 is formed in a groove formed in the housing 10 and provides a static seal for the plate 43.

A scraper 48 is forced against the outer face of the plate 43 by means of a ring 49 and has a leading edge portion which engages the stem portion 16 to prevent the ingress of foreign materials into the bore 12.

An additional bore 50 is formed in the housing 10 and extends perpendicular to the bore 12. A sleeve 52 extends within the bore 50 and is press-fitted over an adaptor plate 54 which is bottomed at the end of the bore. A passage 56 is formed through the housing and connects the operating chamber to a central opening provided through the adaptor plate 54 to permit fluid to pass into and from a bellows 58 connected at one end to the adaptor plate and extending within the sleeve 52. The other end of the bellows 58 is connected to a piston 60 which is slidably mounted in the sleeve 52, with a seal being provided by an O-ring 61 disposed in a groove formed in the piston.

A spring 62 is disposed within the sleeve 52, extends around a stem 63 extending from one face of the piston 60 and engages the latter face of the piston, for urging the piston in an upward direction as viewed in the drawing. A pair of passages 64 and 66 are formed in the housing 10, are spaced apart in a plane perpendicular to the plane of the drawing, and communicate with the bore 50 via corresponding slots provided in the sleeve 52, for reasons that will be explained in detail later.

A plug 68 has an external threaded stem 70 engaging in a corresponding threaded portion at the end portion of the bore 50 to lock the sleeve 52 and its associated components in the bore, with the plug 68 being sealed by means of a ring 72.

An additional bore 74 is formed through the housing 10 in a spaced parallel relation to the bore 50, and has a plate 76 fixed therein to divide the bore 74 into two chambers 74a and 74b. A passage 80 connects the chamber 74a with the groove formed in the housing 10 which accommodates the wick 42. A ball valve 82 is urged against a seat formed at one end of the passage 80 by means of an adaptor 84 and a spring 86 extending in the chamber 74a and between the plate 76 and the adaptor.

The central passage 88 is provided through the plate 76 and is adapted to communicate with the interior of a sleeve 89 disposed within the chamber 74b. A ball valve 90 is supported by an adaptor 92 and is urged in an upward direction against a seat formed at one end of the passage 88 by means of a spring 94 extending in the chamber 74b. A plug 96 closes the end of the bore 74 and has a threaded stem 98 engaging a corresponding threaded portion formed at the end of the bore, with a seal ring 100 sealing the plug in the bore.

It is noted that a clearance exists between the outer surface of the adaptor 84 and the wall defining the corresponding portion of the bore 74, while a ring seal 87 is supported in a groove formed in the adaptor 92 for engaging the corresponding portion of the wall.

An annular chamber 102 is formed in the housing 10 and communicates with that portion of the chamber 74b located above the adaptor 92 by means of a plurality of slots formed in the sleeve 89. The chamber 102 is connected, via passages 104 and 105 formed in the housing 10, to the port 40 and therefore to the reservoir 42. The passages 64 and 66 communicate with the chamber 740 and the passage 104, respectively, for reasons that will be described later.

A passage 106 is formed in the housing 10 and connects the chamber 102 with a bore 108 formed in the end face of the housing, with a porous plug 110 being disposed in the bore 108 and being adapted to pass air but not oil, to provide limited breathing of air which may be drawn into the system.

In operation, the rod 16 and piston 18 are reciprocated relative to the housing 10 in response to high pressure fluid being alternately and selectively supplied to and withdrawn from the operating chambers 20 and 22, with the wick 42 providing a saturable reservoir for capturing extraneous leakage across the outer seal assembly 38. During the occurrence of relative low pressure conditions in the operating chamber 20 as a result of movement of the rod 16 and piston 18 from left to right, the piston 60 will move upwardly in the bore 50 and the bellows 58 will be compressed under the action of the spring 62. This places a partial vacuum in the bore 50 beneath the piston 60 and therefore evacuates the passage 64, and pulls, or lowers, the ball valve 82 from its seat at the end of the passage 80. The vacuum thus draws the fluid from the wick 42 through the passage 80, the chamber 74a, the passage 64, the slots in the sleeve 52, and into the bore 50 beneath the piston 60.

When the actuator cycle is reversed, i.e. when fluid is supplied at relatively high pressure to the operating chamber 20 a portion will pass through the passage 56 and into the bellows 58 to cause same to expand against the force of the spring 62 and force the fluid in the bore 50 below the piston 60 through the slots in the sleeve 52, the passage 64 and into the chamber 74a to force the ball valve 82 into a seated position at the end of the passage 80. The relatively high fluid pressure building up in the chamber 74a and the passage 88 will then force ball valve downwardly against the action of the spring 94 to permit the fluid to pass into the chamber 74b where it passes through the chamber 102 and the passages 104 and 105, to the port 40, and therefore into the reservoir via the conduit 41.

Air breathing and bleeding of any air drawn into the system is provided by the porous plug 110, while the passage 66 provides a relief passage in the event any portion of the system becomes plugged or jammed.

Continued cycling of the actuator provides for the successive withdrawal of the fluid captured by the wick 42 and a forcing of same into the reservoir, and therefore substantially eliminates any extraneous leakage outwardly from the seal assembly 38. As a result, all, or

substantially all, of the external fluid leakage from the actuator will be minimized.

Of course, variations of the specific construction and arrangement of the assembly disclosed above can be made by those skilled in the art without departing from the invention as defined in the appended claims.

I claim:

1. A hydraulic actuator assembly comprising:

a. a housing defining an operating chamber;

b. an actuator rod consisting of a piston portion disposed in said operating chamber and a stem portion connected to said piston portion and disposed in a bore formed in said housing;

c. means to introduce fluid into said operating chamber in a manner to reciprocate said rod relative to said housing;

d. absorbent material means located at the interface between said stern portion and the wall of said housing defining said bore for absorbing fluid leaking from said operating chamber;

e. a storage chamber in said housing;

f. means responsive to fluid pressure conditions in said operataing chamber for directing fluid from said absorbent means to said storage chamber when said rod moves in one direction, and for directing said fluid from said storage chamber externally of said housing when said rod moves in a direction opposite to said one direction;

g. sealing means for said fluid supported by said housing and extending between said operating chamber and said absorbent material means, comprising a pair of spaced sealing members and apassage extending between said sealing members, said passage being exposed at one end to the fluid leaking past said sealing member closest to said operating chamber and being connected at its other end to an outlet for directing said latter fluid externally of said housing.

2. The assembly of claim 1 wherein said storage chamber is formed in said housing and wherein said means for directing fluid from said absorbent means to said storage chamber comprises a first passage fromed in said housing for connecting said operating chamber to said storage chamber, a second piston adapted for reciprocal movement in said storage chamber in response to fluid pressure conditions in said operating chamber and a second passage formed in said housing for connecting said storage chamber to said absorbent material, so that said second piston moves in said storage chamber in one direction to draw fluid from said absorbent means to said storage chamber in response to relative low fluid pressure conditions in said operating chamber, a third passage formed in said housing connecting said storage chamber to said outlet when said second piston moves in the other direction to force said fluid from said storage chamber through said third passage and to said outlet in response to relative high fluid pressure conditions in said operating chamber, a spring disposed in said storage chamber urging said second piston in said one direction said relative high fluid pressure conditions urging said second piston in said other direction, said means responsive to fluid pressure conditions in said operating chamber for directing fluid from said absorbent means to said storage chamber comprising means for creating a vacuum in said storage chamber when said rod is moved in said one direction and means connecting said storage chamber to said absorbent means so that said fluid is drawn from said absorbent material to said storage chamber by said vacuum creating means, said vacuum creating means being adapted to force said fluid from said storage chamber externally of said housing in response to fluid pressure conditions in said operating chamber when said rod is moved in said other direction.

3. The assembly of claim 2 wherein said absorbent means is disposed in a groove formed in said housing.

4. A hydraulic actuator assembly comprising:

a. a housing defining an operating chamber;

b. an actuator rod consisting of a piston portion disposed in said operating chamber and a stern portion connected to said piston portion and disposed in a bore formed in said housing;

c. means to introduce fluid into said operating chamber in a manner to reciprocate said rod relative to said housing;

d. absorbent material means supported by said housing for absorbing fluid leaking from said operating chamber;

e. means for drawing fluid from said absorbent means and for discharging said fluid externally of said housing in response to fluid pressure conditions in said operating chamber when the said rod is moved comprising:

1. a storage chamber;

2. means dividing said storage chamber into first and second chambers;

3. a first channel connecting said absorbent means to the first chamber of said storage chamber;

4. a second channel connecting the second chamber of said storage chamber externally of said housing;

5. a first spring loaded ball check valve closing off the point of entry of said first channel to said first chamber;

6. a third channel through said means dividing said storage chamber into first and second chambers;

7. a spring biased piston in said second chamber;

8. a second ball check valve closing off said third channel at its entry into said second chamber under the force of said piston;

9. means in said housing in respnse to fluid pressure conditions in said operating chamber for creating a vacuum when said rod is moved in one direction and a pressure in response to pressure conditions in said operating chamber when said rod is moved in the other direction;

10. a fourth channel coupling said vacuum means to said first chamber whereby said means creating a vacuum will open said first ball check valve drawing fluid from said absorbent means into said first chamber while at the same time closing off said second check valve and pressure in said fourth channel into said first chamber will cause the fluid therein to open said second check valve causing said fluid to flow into said second chamber and out said second channel externally of said housing.

5. The assembly of claim 4 wherein said means in response to fluid pressure conditions in said operating chamber for creating a vacuum when said rod is moved in one direction and for creating a pressure in response to pressure conditions in said operating chamber when said rod is moved in another direction comprises:

a. a cylinder formed in said housing;

b. a second piston disposed in said cylinder for reciprocal motion therein, dividing said cylinder into an upper and lower portion;

0. a bellows disposed in said upper portion of said cylinder attached to said second piston;

d. a fifth channel coupling the inside of said bellows to said operating chamber;

e. a spring in said lower chamber biasing said second piston upward; and

f. said fourth channel being coupled to the lower portion of said cylinder whereby as the actuator rod is moved in one direction, said second piston will move upward creating a partial vacuum in said lower portion of said cylinder and as the actuator rod moves in the other direction a pressure in said bellows will force said piston downward to apply a pressure in said lower portion. 

1. a storage chamber;
 1. A hydraulic actuator assembly comprising: a. a housing defining an operating chamber; b. an actuator rod consisting of a piston portion disposed in said operating chamber and a stem portion connected to said piston portion and disposed in a bore formed in said housing; c. means to introduce fluid into said operating chamber in a manner to reciprocate said rod relative to said housing; d. absorbent material means located at the interface between said stem portion and the wall of said housing defining said bore for absorbing fluid leaking from said operating chamber; e. a storage chamber in said housing; f. means responsive to fluid pressure conditions in said operating chamber for directing fluid from said absorbent means to said storage chamber when said rod moves in one direction, and for directing said fluid from said storage chamber externally of said housing when said rod moves in a direction opposite to said one direction; g. sealing means for said fluid supported by said housing and extending between said operating chamber and said absorbent material means, comprising a pair of spaced sealing members and a passage extending between said sealing members, said passage being exposed at one end to the fluid leaking past said sealing member closest to said operating chamber and being connected at its other end to an outlet for directing said latter fluid externally of said housing.
 1. A hydraulic actuator assembly comprising: a. a housing defining an operating chamber; b. an actuator rod consisting of a piston portion disposed in said operating chamber and a stem portion connected to said piston portion and disposed in a bore formed in said housing; c. means to introduce fluid into said operating chamber in a manner to reciprocate said rod relative to said housing; d. absorbent material means located at the interface between said stem portion and the wall of said housing defining said bore for absorbing fluid leaking from said operating chamber; e. a storage chamber in said housing; f. means responsive to fluid pressure conditions in said operating chamber for directing fluid from said absorbent means to said storage chamber when said rod moves in one direction, and for directing said fluid from said storage chamber externally of said housing when said rod moves in a direction opposite to said one direction; g. sealing means for said fluid supported by said housing and extending between said operating chamber and said absorbent material means, comprising a pair of spaced sealing members and a passage extending between said sealing members, said passage being exposed at one end to the fluid leaking past said sealing member closest to said operating chamber and being connected at its other end to an outlet for directing said latter fluid externally of said housing.
 2. means dividing said storage chamber into first and second chambers;
 2. The assembly of claim 1 wherein said storage chamber is formed in said housing and wherein said means for directing fluid from said absorbent means to said storage chamber comprises a first passage fromed in said housing for connecting said operating chamber to said storage chamber, a second piston adapted for reciprocal movement in said storage chamber in response to fluid pressure conditions in said operating chamber and a second passage formed in said housing for connecting said storage chamber to said absorbent material, so that said second piston moves in said storage chamber in one direction to draw fluid from said absorbent means to said storage chamber in response to relative low fluid pressure conditions in said operating chamber, a third passage formed in said housing connecting said storage chamber to said outlet when said second piston moves in the other direction to force said fluid from said storage chamber through said third passage and to said outlet in response to relative high fluid pressure conditions in said operating chambEr, a spring disposed in said storage chamber urging said second piston in said one direction said relative high fluid pressure conditions urging said second piston in said other direction, said means responsive to fluid pressure conditions in said operating chamber for directing fluid from said absorbent means to said storage chamber comprising means for creating a vacuum in said storage chamber when said rod is moved in said one direction and means connecting said storage chamber to said absorbent means so that said fluid is drawn from said absorbent material to said storage chamber by said vacuum creating means, said vacuum creating means being adapted to force said fluid from said storage chamber externally of said housing in response to fluid pressure conditions in said operating chamber when said rod is moved in said other direction.
 3. a first channel connecting said absorbent means to the first chamber of said storage chamber;
 3. The assembly of claim 2 wherein said absorbent means is disposed in a groove formed in said housing.
 4. A hydraulic actuator assembly comprising: a. a housing defining an operating chamber; b. an actuator rod consisting of a piston portion disposed in said operating chamber and a stem portion connected to said piston portion and disposed in a bore formed in said housing; c. means to introduce fluid into said operating chamber in a manner to reciprocate said rod relative to said housing; d. absorbent material means supported by said housing for absorbing fluid leaking from said operating chamber; e. means for drawing fluid from said absorbent means and for discharging said fluid externally of said housing in response to fluid pressure conditions in said operating chamber when the said rod is moved comprising:
 1. a storage chamber;
 2. means dividing said storage chamber into first and second chambers;
 3. a first channel connecting said absorbent means to the first chamber of said storage chamber;
 4. a second channel connecting the second chamber of said storage chamber externally of said housing;
 5. a first spring loaded ball check valve closing off the point of entry of said first channel to said first chamber;
 6. a third channel through said means dividing said storage chamber into first and second chambers;
 7. a spring biased piston in said second chamber;
 8. a second ball check valve closing off said third channel at its entry into said second chamber under the force of said piston;
 9. means in said housing in response to fluid pressure conditions in said operating chamber for creating a vacuum when said rod is moved in one direction and a pressure in response to pressure conditions in said operating chamber when said rod is moved in the other direction;
 10. a fourth channel coupling said vacuum means to said first chamber whereby said means creating a vacuum will open said first ball check valve drawing fluid from said absorbent means into said first chamber while at the same time closing off said second check valve and pressure in said fourth channel into said first chamber will cause the fluid therein to open said second check valve causing said fluid to flow into said second chamber and out said second channel externally of said housing.
 4. a second channel connecting the second chamber of said storage chamber externally of said housing;
 4. A hydraulic actuator assembly comprising: a. a housing defining an operating chamber; b. an actuator rod consisting of a piston portion disposed in said operating chamber and a stem portion connected to said piston portion and disposed in a bore formed in said housing; c. means to introduce fluid into said operating chamber in a manner to reciprocate said rod relative to said housing; d. absorbent material means supported by said housing for absorbing fluid leaking from said operating chamber; e. means for drawing fluid from said absorbent means and for discharging said fluid externally of said housing in response to fluid pressure conditions in said operating chamber when the said rod is moved comprising:
 6. a third channel through said means dividing said storage chamber into first and second chambers;
 7. a spring biased piston in said second chamber;
 8. a second ball check valve closing off said third channel at its entry into said second chamber under the force of said piston;
 9. means in said housing in response to fluid pressure conditions in said operating chamber for creating a vacuum when said rod is moved in one direction and a pressure in response to pressure conditions in said operating chamber when said rod is moved in the other direction;
 10. a fourth channel coupling said vacuum means to said first chamber whereby said means creating a vacuum will open said first ball check valve drawing fluid from said absorbent means into said first chamber while at the same time closing off said second check valve and pressure in said fourth channel into said first chamber will cause the fluid therein to open said second check valve causing said fluid to flow into said second chamber and out said second channel externally of said housing. 